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sfitzgerald2
Posts: 1
Registered: ‎02-01-2013

Fluid Flow over an object

636 Views, 9 Replies
02-01-2013 03:26 PM

Hello, 

 

So as the title of my message states, I'm trying to look at the flow of fluid (specifically water) over an object in Autodesk CFD. I've gone through tutorials and looked at other people's examples, but for some reason I still can't get it to work. I've made a virtual flow tank and have placed my object inside of it. I set the material for the object (say abs molded) then set the material for the flow tank (sea water liquid phase). I've placed the flow rate and so forth but for some reason I'm getting an error message stating that "The density of the working fluid is less than or equal to 0". I've gone back and chekd all the data, I've checked the environment data as well and it all seems squared away. Does anyone know what I'm doing wrong? 

 

-Cheers

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Member
harm
Posts: 3
Registered: ‎02-11-2013

Re: Fluid Flow over an object

02-11-2013 06:59 AM in reply to: sfitzgerald2

Hello there, I have exact the same problem, is somthing wrong with setup?

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Product Support
Royce_adsk
Posts: 555
Registered: ‎08-24-2011

Re: Fluid Flow over an object

02-11-2013 01:39 PM in reply to: sfitzgerald2

Hi Sam,

 

What you are running into is actually a known issue.  

 

What I would suggest as a workaround is to create a new material with the same material properties as our Sea Water (Liquid phase), but change the 'Phase' property to 'Variation Method: Vapor Pressure' with a value of 0 instead of the linked Vapor Material.

 

Does that allow your model to work successfully?

 

Thanks,

Royce



Royce Abel
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Member
harm
Posts: 3
Registered: ‎02-11-2013

Re: Fluid Flow over an object

02-13-2013 02:52 AM in reply to: Royce_adsk

Hello, I tried this but it did not solve the problem

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Active Member
aaronlevine
Posts: 6
Registered: ‎02-10-2013

Re: Fluid Flow over an object

02-16-2013 04:44 PM in reply to: sfitzgerald2

Hi,

 

I'm having the same problem. Any idea why this is happening, Royce?

 

Aaron

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Product Support
wildej
Posts: 731
Registered: ‎08-25-2011

Re: Fluid Flow over an object

02-18-2013 06:47 AM in reply to: aaronlevine

Have either of you tried launching from CAD and setting it up again? We have seen this work also.



Jon Wilde
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New Member
samfitz17
Posts: 1
Registered: ‎03-03-2013

Re: Fluid Flow over an object

03-03-2013 04:11 PM in reply to: sfitzgerald2

No I have no tried that yet. I'll go and see if that works tomorrow. Do you know if there are any good video tutorials? I'm trying to simulate flow over hydrofoils and as I've said before, I'm running into some problems. 

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Product Support
wildej
Posts: 731
Registered: ‎08-25-2011

Re: Fluid Flow over an object

03-05-2013 12:08 AM in reply to: samfitz17

Hi,

 

If you have been through the tutorials I would have thought you have most of the knowledge you will need for this.

 

I suggest you consider running in 2D in possible. The more mesh we have with external aero models the better, and utilising the 2D approach can be of great benefit, more mesh, lower runtime.

It would also be worth using Advection Scheme 5 and mesh adaption too.

 

Other than the density issue, are you finding other problems?



Jon Wilde
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New Member
g_wheeler2001
Posts: 1
Registered: ‎09-16-2013

Re: Fluid Flow over an object

09-16-2013 10:45 AM in reply to: sfitzgerald2

Was this issue ever solved? I'm having the same problem.  I was able to run all the tutorials, but when I try my own problem (sea water buoyant flow and convection), I get "The density of the working fluid is less than or equal to 0".

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Product Support
wildej
Posts: 731
Registered: ‎08-25-2011

Re: Fluid Flow over an object

09-17-2013 04:04 AM in reply to: g_wheeler2001
Hi,

Did you try launching from CAD and setting the model up again? This was the only workaround I found to work reliably.
What version of CFD are you running?

Kind regards,
Jon


Jon Wilde
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